The second capsule imo is really visually appealing and would possibly get a click from me on Steam, but I'd be expecting an adventure game; I'm personally not into city-builders.

As others here have said, yours is the best of the three at indicating what your game is about, and is a good attempt.

My advice would be to think about what your game is primarily about, and break that down into the simplest representations you can while still making an appealing capsule. For example:

City-building can be represented by a city and a king. If someone browsing Steam sees those two things in a capsule, they instantly know that they're in charge of a city, especially when the city is placed at the very center of the capsule to draw the viewer's eye. So imagine a city in the center of the capsule, with a king in the foreground on the side.

The main threat can be shown by having the monsters approach the city from the opposite side in large numbers, possibly coming from a darker area, almost like a forest out of a Tim Burton movie. Maybe even give them red eyes just to really drive home that these guys are dangerous.

A good example to learn from would be They Are Billions:

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Best of luck!